A printer as shown in FIGS. 1 and 2 of the accompanying drawings is known, and is so designed as to be connected to a host instrument such as a computer, a word-processor or the like, for printing information from the host instrument onto a recording medium P such as cut-sheets, a continuous form, a set of a plurality of superimposed copying sheets, or the like. The known printer comprises a rotatable platen 1, and a top cover 2 arranged above the platen 1 for movement between open and closed positions. A support shaft 6 is arranged between the platen 1 and the top cover 2 in parallel relation to a longitudinal axis of the platen 1. A plurality of spaced discharge rollers 3 are mounted on the support shaft 6 for rotation therewith in synchronism with the platen 1. The recording medium P is wound about the platen 1 and is clamped between the discharge rollers 3 and a plurality of guide ribs 4 provided on the top cover 2. Rotation of the platen 1 in a normal direction causes the recording medium P wound about the platen 1, to be transported in a normal-feed direction indicated by an arrow a in FIG. 2.
In the conventional printer described above. the discharge rollers 3 are so set as to have their respective peripheral speeds higher than that of the platen 1, to prevent the recording medium P from slackening between the platen 1 and the discharge rollers 3 when the recording medium P is transported in the normal-feed direction. Since, in this manner, the peripheral speed of each discharge roller 3 is set to a value higher than that of the platen 1, there arise the following problems. That is, when the platen 1 is rotated in a reverse direction opposite to the normal direction to transport the recording medium P in a reverse-feed direction indicated by an arrow b, the recording medium P tends to slacken between the discharge rollers 3 and the platen 1, resulting in such anxieties that the recording medium P is contaminated due to contact with the surrounding members or elements and that a bad influence is exerted upon an accuracy with which the recording medium P is fed.